
/* @(#)w_log.c 5.1 93/09/24 */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

/*
FUNCTION
       <<log>>, <<logf>>---natural logarithms

INDEX
    log
INDEX
    logf

ANSI_SYNOPSIS
       #include <math.h>
       double log(double <[x]>);
       float logf(float <[x]>);

TRAD_SYNOPSIS
       #include <math.h>
       double log(<[x]>);
       double <[x]>;

       float logf(<[x]>);
       float <[x]>;

DESCRIPTION
Return the natural logarithm of <[x]>, that is, its logarithm base e
(where e is the base of the natural system of logarithms, 2.71828@dots{}).
<<log>> and <<logf>> are identical save for the return and argument types.

You can use the (non-ANSI) function <<matherr>> to specify error
handling for these functions.

RETURNS
Normally, returns the calculated value.  When <[x]> is zero, the
returned value is <<-HUGE_VAL>> and <<errno>> is set to <<ERANGE>>.
When <[x]> is negative, the returned value is NaN (not a number) and
<<errno>> is set to <<EDOM>>.  You can control the error behavior via
<<matherr>>.

PORTABILITY
<<log>> is ANSI. <<logf>> is an extension.
*/

/*
 * wrapper log(x)
 */

#include "fdlibm.h"
#include <errno.h>

#ifndef _DOUBLE_IS_32BITS

#ifdef __STDC__
    double log(double x)        /* wrapper log */
#else
    double log(x)           /* wrapper log */
    double x;
#endif
{
#ifdef _IEEE_LIBM
    return __ieee754_log(x);
#else
    double z;
    struct exception exc;
    z = __ieee754_log(x);
    if(_LIB_VERSION == _IEEE_ || isnan(x) || x > 0.0) return z;
#ifndef HUGE_VAL
#define HUGE_VAL inf
    double inf = 0.0;

    SET_HIGH_WORD(inf,0x7ff00000);  /* set inf to infinite */
#endif
    exc.name = "log";
    exc.err = 0;
    exc.arg1 = x;
    exc.arg2 = x;
    if (_LIB_VERSION == _SVID_)
           exc.retval = -HUGE;
    else
       exc.retval = -HUGE_VAL;
    if(x==0.0) {
        /* log(0) */
        exc.type = SING;
        if (_LIB_VERSION == _POSIX_)
           Djy_SaveLastError(ERANGE);
        else if (!matherr(&exc)) {
           Djy_SaveLastError(ERANGE);
        }
    } else {
        /* log(x<0) */
        exc.type = DOMAIN;
        if (_LIB_VERSION == _POSIX_)
           Djy_SaveLastError(EDOM);
        else if (!matherr(&exc)) {
           Djy_SaveLastError(EDOM);
        }
            exc.retval = nan("");
        }
    if (exc.err != 0)
           Djy_SaveLastError(exc.err);
        return exc.retval;
#endif
}

#endif /* defined(_DOUBLE_IS_32BITS) */
